Normal mammalian saliva has a low osmolarity and ionic strength which play important roles in oral biology and are altered in several diseases. The low NaCl concentration of saliva results from active Na+ reabsorption in the duct system of the salivary gland. However, much has been learned about this reabsorption process through the study of isolated, luminally perfused salivary duct preparations. The small size and geometry of this organ complicates further investigation on the cellular mechanisms of this transport and its regulation. Thus, the proposed pilot project seeks to evaluate a potential model epithelium - the allantoic epithelium of the chick embryo - which is readily available in large sheets and has a Na+ absorption process which is probably measurable as the short circuit current (SCC) and appears to be similar to that in salivary ducts. The project addresses the following aims: 1) to verify equality between net Na+ flux and the SCC; 2) to study the effects of mineralocorticoids on Na+ transport and compare with published results for salivary ducts; 3) to determine the effects of autonomic nervous system agonists and neuropeptides (e.g., VIP) on Na+ transport and compare with published results for salivary ducts; 4) to do the above experiments at two development ages, which may relate to postnatal changes in saliva production mechanisms. The combined results of this pilot project will be evaluated to ascertain the suitability of the allantoic epithelium as a model system relating to salivary duct transport processes.